Bronchial vascular reabsorption of low-protein interstitial edema liquid in perfused sheep lungs

Previously, we quantified reabsorption of interstitial pulmonary edema liquid into the pulmonary circulation during recovery from hydrostatic edema. To determine whether the bronchial circulation also reabsorbs edema liquid, we induced very-low-protein interstitial edema in seven sheep lungs by perfusion of the pulmonary circulation with diluted blood and 1% albumin in Krebs-Henseleit buffer containing 125I-labeled albumin for 70 +/- 40 min. In eight control sheep we perfused the lungs with diluted blood and 5% albumin in Krebs-Henseleit buffer containing 125I-albumin without causing significant edema formation. Subsequently, we washed the intravascular tracer from the pulmonary circulation with buffered saline and then perfused the bronchial vessels via the bronchoesophageal artery with whole or diluted blood (normal protein osmotic pressure). We measured flow, hematocrit, and 125I-albumin concentration in the venous outflow into the left atrium and into the azygos vein for 2 h. We calculated the volume of liquid reabsorbed on the basis of the change in hematocrit and 12I-albumin concentration in the outflow. On the basis of hematocrit dilution, the net clearance of interstitial liquid (edema minus control) averaged 21 ml (15% of the induced edema). One the basis of 125I-albumin reabsorption, the net clearance of interstitial liquid was 12 ml. We conclude that the bronchial circulation may be a clearance route for interstitial liquid and protein during recovery from low-protein hydrostatic edema.